Basin Marshes usually develop in large solution depressions that were formerly shallow
lakes. The lake bottom has slowly filled with sediments from the surrounding uplands and with
peat derived from plants. Thus, the soils are usually acidic peats. The hydroperiod is generally
around 200 days per year. Open areas of relatively permanent water within the marsh, with or
without floating aquatic vegetation, are considered to be Marsh Lakes (See Lacustrine Natural
Communities).

Fire maintains the open herbaceous community by restricting shrub invasion. The
normal interval between fires is 1 to 10 years, with strictly herbaceous marshes burning about
every 1 to 3 years, and those with substantial willow and buttonbush having gone 3 to 10 years
without fire. Fires during drought periods will often burn the mucky peat and will convert the
marsh into a Marsh Lake.

Basin Marshes are associated with and often grade into Wet Prairie or Lake communities.
They may eventually succeed to Bog, if succession is not reversed by a muck fire. Many of the
plants and animals occurring in Basin Marshes also occur in Floodplain Marsh, Slough, Swale
and Depression Marsh. Large examples of the Depression Marsh, in fact, may be very difficult
to distinguish from small examples of Basin Marsh.

Normal hydroperiods must be maintained, or Basin Marsh vegetation will change.
Shortened hydroperiods will permit the invasion of mesophytic species, while longer
hydroperiods will convert marsh into lake. Fire is also necessary to control hardwood
encroachment. However, fires during droughts should be avoided to reduce the possibility of a
muck fire. Many sites have been degraded by pollution or drained for agricultural uses.